Vertical MOS transistor are sufficiently known and described for example in Stengl/Tihanyi: “Leistungs-MOSFET-Praxis”, [“Power MOSFETs in practice”], Pflaum Verlag, Munich, 1994, pages 29 to 40. Given suitable driving, in the case of vertical components of this type, a current-carrying path runs between a drain zone and a source zone in a vertical direction perpendicular to a front side and a rear side of a semiconductor body/semiconductor chip in which the component is integrated. The driving is effected via a gate electrode, which is arranged in a manner insulated from the semiconductor body and adjacent to a body zone situated between source and drain.
In the case of so-called trench transistors, the gate electrode is arranged in a trench extending into the semiconductor body proceeding from one of the sides. In the case of these trench transistors, the source zone is usually situated in the region of the front side of the semiconductor body, proceeding from which the trench extends into the semiconductor body. The drain zone is usually situated in the region of the rear side remote from the front side, a drift zone doped more weakly than the drain zone usually being arranged between the drain zone and the body zone in the case of power transistors.
Vertical MOS transistors are used as power transistors in a wide variety of areas. One area of application is switching converters, in which power transistors driven in clocked fashion are used for regulating the power consumption of the switching converter, and thus for regulating the output voltage.
One crucial operating parameter of such MOS power transistors is the on resistance thereof (Ron), which denotes the electrical resistance between drain and source when the component is driven into the on state, and the gate-drain capacitance thereof (CGD), which denotes the parasitic capacitance between the gate electrode and the drain zone or the drift zone—adjacent to the drain zone—of the component.
In the case of components of this type, a reduction of the on resistance can be achieved by providing so-called field plates that are at gate potential. In the case of trench transistors, by way of example, a field plate, which may be formed integrally with the gate electrode, is in this case arranged in the trench below the gate electrode and adjacent to the drift zone. Such a component is described for example in U.S. Pat. Nos. 4,941,026 or 5,973,360.
The provision of a field electrode that is at gate potential increases the gate-drain capacitance, so that U.S. Pat. No. 5,283,201 or US 2003/0073287 A1 proposes providing a field electrode which is separate from the gate electrode and is at a potential that differs from the gate potential, for example source potential.